Method of making thyristor having low reflection light-triggering structure

Abstract

A thyristor having low-reflection light-triggering structure. In a light-triggerable thyristor, pyramidal depressions are formed in a simple manner by a preferred etching method, being formed in the region of the photon entry face in order to produce a low-reflection light-triggering structure. Incident light is absorbed in the pyramidal depressions largely independent of the wavelength of the incident light and nearly completely. The low-reflection light-triggering structure thereby produced can be formed with relatively little outlay. This is especially true when a defined overhead ignition voltage is simultaneously set by the pyramidal depressions.

What is claimed is: 
     
       1. A method for manufacturing a thyristor having a low-reflection light-triggering structure, the structure having a sequence of semiconductor layers of alternating conductivity types that has a p-emitter to which is electrically connected an anode electrode, an n-base, a p-base and an n +  -layer having recesses for an n-emitter to which is electrically connected a cathode electrode and for an auxiliary emitter, comprising the steps of: providing a 55 100}- wafer; covering the {100}- wafer by an etching mask having quadratic mask openings aligned in <110>direction relative to the crystal lattice; forming pyrmaidal depressions by anisotropic etching of the {100}- wafer; a low-reflection photon entry face being formed by the pyramidal depressions at the photon entry face, whereby the reflectivity is largely independent of the wavelength of light incident on the photon entry face; and forming an overhead ignition-resistant thyristor having defined overhead ignition voltage substantially by the pyramidal depressions before doping of the p-base, so that a doping boundary surface between the p-base and the n-base follows the surface contour of the photon entry face.